Running a modern engine, gas or diesel, less than full throttle in a tractor does in fact cause additional wear for several reasons. The "old" days of how your father's father or whatever ran a tractor are well past. Modern engines running on ULSD must be run at full throttle as designed for the application. Running at less than full throttle while even doing light work causes excess heat or not enough heat in an engine depending on the load. This in turn leads to carbon build-up and valve problems. This is especially true of tier 3 and 4 emission compliant engines. In fact, even a Cummins or International over the road diesel run on an in-town delivery truck will have problems unless taken out on the highway and "opened-up" to higher RPMS. Google the relatively new "International MaxxForce" diesels and read about the problems they are having with them in applications that do not see high RPM loads such as in-town delivery, airport shuttle and school bus applications.
The newest tier 4 and IIIB engines use EGR (exhaust gas recirculation) and many use DPF (diesel particulate filters) which require an engine run at a higher temperatture then "older gen" diesels.
Basically the "crap" that diesels used to exhause now gets puked back into the engine and "recirculated".
From the Kubota web page >>>>>""Tier 4 and Stage IIIB are extremely stringent standards. The new standards require further reduction of particulate matter (diesel soot) by 90% in comparison to the previous standards.
In order to comply with the new standards, Kubota utilized a variety of technologies such as Common Rail System, an electronic fuel injection system, for optimization of combustion processes, Exhaust-Gas-Recirculation Device (EGR)*3 and Diesel Particulate Filter (DPF)*4 for improvement of emission performance . These technologies will bring more durable, quieter and fuel efficient engines with minimal impact to the engine package for ease of installation into OEMs machines.
In additional to the above, Kubota also developed and introduced a new emission-compliant diesel engine (engine output range between 19 to 37kW), which utilizes Kubotaç—´ proprietary "TVCS"*5 combustion system and unique DPF regeneration system.
Kubota also obtained EPA and CARB certifications for diesel engines with an output range below 19kW. Of special note is that Kubota obtained the emission certifications without adding new devices, but with further optimization and improvement of existing technologies.
With the introduction of these newly developed diesel engines, Kubota is confident to satisfy both the emission standards as well as the markets wide-variety and challenging demands.
Production of these new emission certified engines will begin in October 2012 for use in Kubota branded agricultural and construction machineries as well as OEMç—´ equipment such as construction machines, gen-sets, welders and other industrial applications.
*3?GR: Technique to reduce NOx by re-circulating a portion of exhaust gas to the engine cylinder and reducing the oxygen content to a lower combustion temperature""<<<<
A modern Diesel engine has a narrow RPM band for proper and efficent operation. On most modern tractors in order to achieve the proper PTO speeds the engine is designed for full throttle operation. Anything less during a load runs the risk of lugging and creating excess heat and stress on the engine and / or too low of cylinder head temps resulting in excess carbon, emissions systems problems and ultimately valve train issues.
More importantly than the engines, which are almost bullet proof anyway, is the hydro pumps. they are designed for a specific RPM and tractors / ztr mowers ect are designed around the pumps. Even if doing light work the tractor itself doesn't get any lighter and has to be moved around regardless of what you might be doing with it...even just driving it down the drive way. The hum you hear with hydro pumps at low RPMs is lugging of the pumps and I promise you will see significantly reduced longevity on pumps run at less that full throttle.
Also, when running an engine and hydro pumps at less than full RPMs the following occurs:
--less oil pump volume circulating and less pressure for both lubrication and cooling (this applies to both engines and hydros....in an engine it might even under some circumstances cause a lack of lubrication / burned valves and failure)
--less engine coolent being circulated through the radiator (the water pump is RPM driven, same as oil pump)
--excessively high or low cylinder head temps causing multiple problems as stated above / carbon build up
--harmonic vibrations that can damage the tractor or even frame....diesel produce destructive harmonic vibrations that can even crack frames and welds. If running a unit at less than full throttle which is what it is designed for you may cause the vibrations to occur (you may or may not even feel them) and can damage your tractor
--damage to implements that require 540 PTO / I have seen so many people using rotary and finish mowers at less than the 540 spec / this causes increased wear to the gear boxes ect
Nothing good comes from excess idling and running a modern diesel at less than full RPMS as designed.
Older diesels are different just like older carburetor cars needed the throttle pumped to set the choke and modern fuel injection does not.
I know there will be antidotal evidence to the contrary of what I have said....someone out there has run at less than full throttle for years and thousands of hours without problems ect or maybe the problems just have not shown up yet. It like having high cholesterol...you wont necessarily see the problems until later and with a diesel that could be into the thousand plus hr mark. I can show you an example of a 89yeor old pack to 2 pack a day smoker that is healthy.....there is always an exception!
I have an older BX that I keep at my shop and run a PTO generator with day in and day out at 540 PTO which means 3150ish engine RPMs. I have had 'Bota diesels hit the 10,000 hr mark and still run.
I stand by run it at full RPM and the work / rebuilds my shop saw over the years confirms this as well as every dealer training session I have been to on Kubota, Yanmar, Cat, Kohler, Brigss, Kawasaki ect.
